Peng Chaoyong, Yang Jiansi, Zheng Yu, Xu Zhiqiang, Jiang Xudong
Institute of Geophysics, China Earthquake Administration, No. 5 Minzudaxue South Road, Haidian District, Beijing 100081, China.
Sci Rep. 2014 Oct 27;4:6770. doi: 10.1038/srep06770.
More and more earthquake early warning systems (EEWS) are developed or currently being tested in many active seismic regions of the world. A well-known problem with real-time procedures is the parameter saturation, which may lead to magnitude underestimation for large earthquakes. In this paper, the method used to the MW9.0 Tohoku-Oki earthquake is explored with strong-motion records of the MW7.9, 2008 Wenchuan earthquake. We measure two early warning parameters by progressively expanding the P-wave time window (PTW) and distance range, to provide early magnitude estimates and a rapid prediction of the potential damage area. This information would have been available 40 s after the earthquake origin time and could have been refined in the successive 20 s using data from more distant stations. We show the suitability of the existing regression relationships between early warning parameters and magnitude, provided that an appropriate PTW is used for parameter estimation. The reason for the magnitude underestimation is in part a combined effect of high-pass filtering and frequency dependence of the main radiating source during the rupture process. Finally we suggest only using Pd alone for magnitude estimation because of its slight magnitude saturation compared to the τc magnitude.
越来越多的地震预警系统（EEWS）正在世界许多地震活跃地区开发或目前正在进行测试。实时程序中一个众所周知的问题是参数饱和，这可能导致对大地震震级的低估。在本文中，利用2008年Mw7.9级汶川地震的强震记录，探讨了应用于Mw9.0级东北冲地震的方法。我们通过逐步扩大P波时间窗（PTW）和距离范围来测量两个预警参数，以提供早期震级估计和对潜在破坏区域的快速预测。这些信息在地震起源时间后40秒即可获得，并可在随后的20秒内利用更远台站的数据进行完善。我们表明，只要使用适当的PTW进行参数估计，预警参数与震级之间现有的回归关系是适用的。震级低估的部分原因是破裂过程中高通滤波和主要辐射源频率依赖性的综合影响。最后，我们建议仅使用Pd单独进行震级估计，因为与τc震级相比，其震级饱和程度较小。
